Package delivery trucks, which have also been referred to as panel trucks and vans, typically have one or more sliding doors. By gripping a door handle on the inside or outside, the door may be manually moved between positions closing and opening a doorway in the truck body. These doors typically have a latch coupled with the two handles which holds the door in a fully opened or fully closed position by engagement with strikes mounted adjacent each end of the door run above its track. The door in its closed position may thus be unlatched and slide open from either side of the door by rotation and pulling the inside or outside handle. For security these latches have also been provided with manually operable inside locks which prevent the door from being opened from the outside while a worker is inside. This has commonly been in the form of a lock bar that may be moved into and out of locking engagement with an internal cam that is operated by the outside handle that cams the latch out of latching engagement with a strike. Exemplifying such sliding door latches are those latches of the model 4000 series that have been sold for the past 30 years by Kason Industries, Inc. of Shenandoah, Georgia.
A persistent problem associated with these sliding door latches has been their propensity to lock out authorized users by accident. Too often a worker who has locked the latch while working inside the vehicle will forget to unlock it upon his departure. Once outside the vehicle the worker can slide the door shut, even using the outside handle, whereupon he or she is now unintentionally locked out.
Heretofore efforts to incorporate a lock self-cancelling feature into sliding door latches have been made but without practical, commercial success. These efforts have involved more costly designs with retrofit inability. Thus there has long existed a need for a sliding door latch with an inside lock that has means for automatically canceling or unlocking the latch lock upon the latch being operated over the strike after having locked. It is to the provision of such that the present invention is primarily directed.